Question: Tiffany just found beautiful yarn for 20 percent off at her favorite yarn store. She can make 1 scarf from $\frac{4}{5}$ of a ball of yarn. If Tiffany buys 20 balls of yarn, how many scarves can she make?
Answer: We can divide the balls of yarn (20) by the yarn needed per scarf ( $\frac{4}{5}$ of a ball) to find out how many scarves Tiffany can make. $ \dfrac{{20 \text{ balls of yarn}}} {{\dfrac{4}{5} \text{ ball per scarf}}} = {\text{ number of scarves}} $ Dividing by a fraction is the same as multiplying by the reciprocal. The reciprocal of ${\dfrac{4}{5} \text{ ball per scarf}}$ is ${\dfrac{5}{4} \text{ scarves per ball}}$ $ {20\text{ balls of yarn}} \times {\dfrac{5}{4} \text{ scarves per ball}} = {\text{ number of scarves}} $ ${\dfrac{100}{4}\text{ scarves}} = 25\text{ scarves}$ Tiffany can make 25 scarves.